Studies on Micro and Ultrafiltration in oily wastewater purification

A series of ultrafiltration (UF) and microfiltration (MF) tests were performed on an oily wastewater mixture whose composition closely resembled that of wastewaters accumulating in a ship's bilge. The wastewater was found to contain a substantial amount of dissovled solids, defined as particles measuring less than 0.45 micron, which cannot be accounted for as dissolved salts alone. These oily wastewaters are by nature difficult to treat with membrane processes. The presence of used lubricating oils in a ship's bilges implies that particles of soot will be present in this wastewater. In order to offer a better representation of actual bilge water, synthetic wastewater mixtures were prepared using used lubricating oils. Experimental results indicate that free oil is present in this type of wastewater. The wastewater was found to contain mechanical emulsions, chemical emulsions and particles of soot that can act as nuclearing sites for oil. The size of the particles causing the flux decline was determined from cake filtration theory. TRUNCATED